Rates, Dates and Geologic Time: Teaching about the Temporal Aspects of Geoscience

Hierarchical Alignment of Temporal Magnitude

Ilyse Resnick, Psychology Department, Temple University

One challenge in teaching and learning about time is the disconnect between the linear scale of time and how temporal information is cognitively represented. Humans unitize time. We segment the continuous flow of time into events, with discrete beginnings and ends (Shipley & Zacks, 2008). This representation is adaptive, as it allows humans to compare different experiences. The sequence within an event is predictable (e.g. dinosaurs exist in the Mesozoic Era), and the event ends when things do not follow that same pattern of predictability (e.g. the Cretaceous -Tertiary Extinction event when dinosaurs became extinct). Thus, an event becomes a local region of predictability (Shipley & Zacks, 2008).

The category adjustment model of recall suggests that memory for when an event occurred is stored as a hierarchical combination of metric and contextual information (Huttenlocher, et al., 1988). The retrieval of any lower level information implicitly contains the boundaries of any associated higher level units (Huttenlocher, et al., 1988). For example, remembering that dinosaurs first appeared in the Triassic Period implicitly contains information that dinosaurs also first appeared during the Mesozoic Era. However, in the absence of exact information, people use boundaries of other events to help make estimations. Variation in estimation, therefore, occurs because of the imprecision of event boundaries (Shipley & Zacks, 2008). The more imprecise or the larger the boundaries, the more variation one could expect to find (Huttenlocher, et al., 1988; Shipley & Zacks, 2008). Without information at a lower level then estimations must default to a higher level. For example, if a student cannot recall which period dinosaurs first appeared, but can recall it happened in the Mesozoic Era, their estimation of a date will range 180 million years from the Triassic period to the Cretaceous period.

The placement of event boundaries will systematically distort estimations in predictable ways. People tend to remember events at boundaries more clearly than those in between. Subjective experience of magnitude is also influenced by the number of event boundaries that a person can recall; the more boundaries a person can recall the greater the subjective magnitude, and the converse for the recollection of a smaller number of boundaries. Subsequently, regions sparsely populated with events will elicit more variation in estimation of location and an underestimation of magnitude.

The hierarchical alignment model aims to alleviate distortions of temporal magnitude by fostering a linear representation of time, populated with boundary information at that scale (Resnick, et al., 2011).

The hierarchical alignment model is based on the progressive alignment model of analogical reasoning (Kotovsky & Gentner, 1996). The progressive alignment model advocates the comparison of two similar items. Comparing two similar items helps extend the analogy to unfamiliar items by making corresponding relations more salient. The progressive alignment of scales may alleviate the conceptual dissimilarity between human scales and extreme scales by providing greater structural alignment across changes of scale. The hierarchical alignment model extends the principles of the progressive alignment model to include the hierarchical organization of all previous alignments. The hierarchical organization highlights how each alignment is related to the others. Specific to understanding temporal information, the hierarchical organization will help populate each scale with boundary information by providing internal structure of magnitude relations within event boundaries.

In a study on teaching geologic time, the hierarchical and progressive alignment of time was found to be an effective way to reduce magnitude-based errors in understanding geologic time (Resnick, et al., 2011). The hierarchical alignment activity had students align time to space beginning with a familiar personal time scale, then work through different historic and geologic timelines, up to the full Geologic Time Scale. For each timeline, students were required to indicate the timeline's length, locate specific events, and locate where all previous timelines would begin on the current timeline. The students who completed the hierarchical alignment activity demonstrated a more accurate sense of the relative durations of geological events and a reduction in the magnitude of temporal location errors relative to those who did not. Importantly, all students received the same content and amount of practice aligning time to space in a stratigraphy lab.

The results of the hierarchical alignment intervention are consistent with students developing coherent nested temporal categories to approximate a linear representation of time. The hierarchical alignment intervention is specifically designed to control for common issues with analogies, such as failure of alignment and unrelated salient features (Kotovsky & Gentner, 1996), by keeping everything aligned except for magnitude information.Thus, the hierarchical alignment intervention may be a more effective teaching tool than current practices employing single analogical mapping exercises.

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